Preliminary Results of Semi-Sitting Retrosigmoid Surgery for Vestibular Schwannomas from a North American Skull Base Practice

Background/Rationale: The semisitting position for surgical treatment of vestibular schwannomas is under-represented in North America. We changed the practice at our institution from supine to semisitting position for retrosigmoid approaches. We hypothesized semisitting position demonstrates shorter operative time and better facial nerve function when accounting for tumor size.

Methods: This is a retrospective review after a prospective change in practice. In 2018, all fellowship-trained skull base neurosurgeons at our institution changed to using only semi-sitting positioning for retrosigmoid approaches for vestibular schwannomas. We compared results with supine retrosigmoid and translabyrinthine surgeries regarding operative time, postoperative House–Brackmann (HB) scale, cerebrospinal fluid leaks, and other surgical complications.

Results: From January 2014 to March 2019, a total of 71 patients underwent first-time resection for vestibular schwannoma. Thirty-seven patients underwent surgery via translabyrinthine approach, 14 had supine retrosigmoid approach, and 20 had semisitting retrosigmoid approach. Mean operative time for tumors under 2.5 cm was 247 minutes for semisitting retrosigmoid, 399 minutes for supine retrosigmoid approach, and 383 minutes for translabyrinthine approaches (p = 0.009). Mean operative time for tumors over 2.5 cm was 420 minutes for semisitting approach, 502 minutes for supine retrosigmoid approach, and 513 minutes for translabyrinthine approaches (p = 0.024). For tumors under 2.5 cm, immediate postoperative HB scale was 1 to 2 in 71.4% of patients in the semisitting group, compared with 60% in the supine group and 69.6% in the translabyrinthine group, while at 6 months 85.7% of semisitting patients had HB 1 to 2 facial nerve function, compared with 80% in the supine group and 82.6% in the translabyrinthine group. For tumors over 2.5 cm, immediate postoperative HB scale was 1 to 2 in 53.8% of patients in the semisitting group, compared with 66.7% in the supine group and 71.4% in the translabyrinthine group, while at 6 months 69.2% of semisitting patients had HB 1 to 2 facial nerve function, compared with 77.8% in the supine group and 71.4% in the translabyrinthine group. For tumors less than 2.5 cm, 14.3% of semisitting patients had a postoperative cerebrospinal fluid leak compared with 20% for supine patients and 17.4% for translabyrinthine patients. For tumors over 2.5 cm, 30.8% of semisitting patients had a postoperative cerebrospinal fluid leak compared with 11.1% for supine patients and 21.4% for translabyrinthine patients. There were no significant intraoperative venous air embolus events in any of the groups.

Conclusion: Our data demonstrate statistically significantly shorter operative time using semisitting approach. Semisitting position demonstrates an equivalent percentage of patients with HB grade 1 and 2 facial nerve functions at 6 months for tumors under 2.5 cm, but not for tumors over 2.5 cm. Cerebrospinal fluid leak rate was lower in the semi-sitting group for tumors under 2.5 cm, but higher for tumors over 2.5 cm. The shorter operative time is likely due to ability of the surgeon to perform bimanual dissection while removing tumor, rather than holding a suction in one of their hands at all times. The advantage of our study is that the surgeons serve as their own controls when comparing the results of semi-sitting and supine retrosigmoid approaches.